Staff Sergeant Brad Fasnacht was clearing mines on an Afghan road a year ago when an IED blast broke his spine and both ankles and put him in a two-week stupor that ended only when he woke up, 7,000 miles away, at Walter Reed Army Medical Center in Washington. The explosion had knocked his helmeted head so violently, he suffered a traumatic brain injury, which exacerbates his posttraumatic stress disorder (PTSD). Although Army doctors and nurses have been able to get the 26-year-old walking again, he has had to call in a specialist  Sapper, an Australian cattle dog mix  to help tackle his PTSD. (See a video of dogs helping veterans cope with PTSD.)

"He has changed my life," Fasnacht says of the 1-year-old mutt, whose name is shorthand for "combat engineer," Fasnacht's Army job. Sapper goes with him whenever he leaves his Silver Spring, Md., apartment, something he was terrified of doing until he got his canine companion in April. Three combat tours and two Purple Hearts had left him in a state of hypervigilance, constantly scanning suburban streets and trees for snipers. War had made him wary of crowds  and even of individuals who got a little too close. "I'd just freak out, getting really uneasy," he says. "But not anymore." The speckled dog calms Fasnacht's anxieties and keeps them from mushrooming into panic attacks. Part bodyguard, part therapist, Sapper also serves as an extra set of eyes and ears. "I've lost some of my hearing, but Sapper alerts me if someone is coming up behind me," he says. When Fasnacht is sleeping, the dog will wake him from a nightmare by licking his face.

As researchers test high-tech PTSD treatments (such as hyperbaric oxygen chambers and virtual-reality exposure therapy), a low-tech alternative is emerging in the form of man's best friend. Although the government has been providing service dogs to troops who have lost their sight or suffered other physical injuries, it is only beginning to look into whether these animals can improve the lives of those who are psychically injured. The need for good treatment options is enormous: some 40,000 troops have been physically wounded in Afghanistan and Iraq, but 10 times as many exhibit symptoms of PTSD. (See pictures of the U.S. Marines' offensive in Afghanistan.)

Amid all this hard-to-heal pain, veterans and dog-training organizations, some with playful names like Patriot Paws and Hounds4Heroes, are rushing to pair wounded vets with trained canines. One of the leaders of this movement, Dave Sharpe, 31, was so traumatized during deployments to Saudi Arabia and Uzbekistan that his anxiety and recurring nightmares kept him largely confined to his Yorktown, Va., home. "I was always looking for a fight," he says. "I was beating on the walls." But he says all that changed when a friend encouraged him in 2002 to visit an animal-rescue shelter, where he spied 2-month-old Cheyenne. Not long after he adopted the brown and white pit bull mix, Sharpe had another dream about the Taliban sympathizer who pulled a gun on him. When Sharpe woke up in a cold sweat, the dog was watching him. "What are you looking at?" he recalls yelling. Cheyenne barked in response, and after he told her to shut up, she barked again, prompting him to wrap her in his arms, collapse on his bed and tell her everything that was weighing on his mind. "I just lost it," he says. "I have no idea why, but I felt completely at ease."

Sharpe credits the dog for such a dramatic improvement in his PTSD that he went on to found the nonprofit P2V  short for Pets2Vets  last year. Since then, he has been sharing his story with soldiers, cops, firefighters, first responders  people who could use their own Cheyenne  and has given dogs to Fasnacht and some 20 other vets. His promise to servicemen and -women in need: "We'll get you your pet within a month, maximum."

Not everyone is convinced such quick pairings are a good idea. For starters, it's still an open question whether dogs actually help alleviate PTSD. Both the VA and the Army are launching studies designed to confirm widespread anecdotal evidence that the benefits are real. And if they are, the next big question is whether shelter dogs like Sapper, who took two weeks and $350 to train, provide as much relief as specially trained dogs, which take two years  and up to $35,000  before they are ready to be paired with a wounded vet. "I really believe the dogs can provide tremendous benefits," says Minnesota Senator Al Franken, who authored a law ordering the VA to study dogs' effects on PTSD sufferers. "The whole point of this is to measure in a scientifically valid way what the benefits are of service dogs to vets with psychological injuries and make a better life for these guys and women who have put everything on the line for us."